Identificação de fragilidades nas sub-bacias hidrográficas de Lorena/SP: contribuições à conservação dos recursos hídricos e ao planejamento ambiental

Abstract

The intensive exploitation of natural resources and inadequate environmental planning are factors that intensify environmental vulnerabilities, including the degradation of water resources. This reality highlights the need for territorial planning that incorporates tools capable of guiding conservation actions and integrated environmental and water management. In this context, Geographic Information Systems (GIS), combined with multicriteria analysis methods such as the Analytic Hierarchy Process (AHP) and the application of fuzzy logic membership functions, become essential to support decision-making, enabling more precise and well- founded judgments. Given this scenario, the present study aimed to identify the environmental and water-related vulnerabilities of the sub-watersheds in the municipality of Lorena, located in the interior of the State of São Paulo, with the goal of supporting water resource conservation and local environmental planning. Additionally, two methodologies were compared in this identification process: overlay using arithmetic mean (referred to as the traditional method) and the AHP method combined with fuzzy membership functions. The methodology was initially based on a systematic literature review to select relevant environmental themes, which were defined as slope, land use, pedology, rainfall, and permanent preservation areas (PPA). Subsequently, for rainfall, two distinct climatic scenarios were analyzed: high rainfall intensity and water scarcity. The sensitivity analysis confirmed the relevance of the selected themes, and the water scarcity scenario was adopted as a reference for mapping. Thematic maps of the sub- watersheds were created using Quantum GIS (QGIS) software, followed by reclassification of the degrees of vulnerability (very low, low, moderate, high, and very high). In the traditional method, a simple arithmetic mean was applied; in the AHP method, differentiated weights were assigned based on expert evaluation. The results showed significant differences between the methods. The arithmetic mean tended to homogenize the data, smoothing out environmental variations. In contrast, the AHP method combined with fuzzy membership functions allowed for a more detailed and accurate representation of territorial conditions, highlighting areas under greater anthropogenic pressure and regions with preserved vegetation. It was concluded, therefore, that the integration of fuzzy membership functions and multicriteria methods represented an effective and improved methodological approach for analyzing environmental and water vulnerability, especially in complex territories. The final product obtained has the potential to support strategic actions for environmental management and planning, water resource conservation, and the formulation of public policies in the municipality of Lorena.